Safety mechanism for pneumatic fastener driving machines



Jan. 20, 1970v w. LANGE ETAL SAFETY MECHANISM FOR PNEUMATIC FASTENERDRIVING MACHINES 3 Sheets-Sheet 1 Filed Feb. 26, 1968 fnz/ewrsx- Wdfredla 19 66567 1/ 0 Nam/mm? 3 Z 5 3% x g a J 0 2 8% 2 Z 21 H \1 lhhh. L 3/w :Z .4 6 3 m /3 Z 2 2 W I 5 I ham ,5 H 1 w 5 Jan. 20, 1970 W. LANGEETAL 3,490,545

SAFETY MECHANISM FOR PNEUMATIC FASTENER DRIVING MACHINES Filed Feb. 26,1968 3 Sheets-$heet 2 f ,7 :u' 1 37 1 W "i 3 I 25 27- g'y 23 J 34 V 7 535 Y 16 9 .20 6 r 4 22 L 1? 15 i I 17 I i 1Q J3 12- E l w [M 5; i

SAFETY MECHANISM FOR PNEUMATIC FASTENER DRIVING MACHINES 5 Sheets-Sheet3 Filed Feb. 26, 1968 United States Patent Olfice rm. 01. B271? 7/06;azsd 17/10; F15b 20/00 U.S. (1173-2 8 Claims ABSTRACT OF THE DISCLOSUREIn a compressed air operated hand tool for driving staples and similarfasteners having a safety trip member for the manually actuable triggerof the control valve, the trip member is controlled by placing the toolagainst a workpiece, and its upper end being provided with a piston inthe inoperable position of the tool is under the influence of compressedair and keeps the trip member in the position in which the trigger isblocked, whereby when the trip member gets in operative position thecontrol valve is pneumatically opened by a slight movement of thetrigger.

DESCRIPTION The present invention relates to a safety mechanism forpneumatically operated hand tools for driving fasteners, such asstaples, nails, pins, and the like.

It is common practice to provide pneumatic driving machines with asafety mechanism, which blocks the manually actuated control valve andprevents it from being accidentally operated unless the machine is inits operative position and placed with its ejector against a workpiece,into which the fastener is to be driven. The prior art safety mechanismscomprise lever means and require a large effort for releasing andactuating the control valve, thus reducing the efficiency and speed ofoperation of the machine.

Accordingly, it is an important object of the present invention toprovide a simple and easily operable safety mechanism which enables ahigh working capacity of the machine as well as a quick sequence ofdriving strokes.

Another object of the invention is to provide a pneumatic actuation ofthe safety mechanism, in order to produce a working stroke also whenmoving the trigger assembly of the control valve with low finger forceand small stroke, as soon as the safety trip member has been renderedineffective by placing the ejector against the workpiece.

Still a further object of the invention is the provision of a safetymechanism of the above-mentioned kind which is of simple and practicallytrouble-free construction.

These and other objects of the invention will be readily apparent fromthe following detailed description in conjunction with the accompanyingdrawings, in which:

FIGURE 1 is a fragmentary side elevational view of a pneumatic fastenerdriving hand tool embodying features of the invention and with certainparts thereof broken away and in section, showing the machine in itsinitial or inoperative position,

FIGURE 2 is the machine of FIG. 1 in its operative position aftercompleted working stroke,

FIGURES 3, 4, 5 and 6 are fragmentary sectional views of a modifiedarrangement of the safety mechanism shown in difierent positions.

The invention pertains to a compressed air actuated hand tool comprisinga cylinder being, by way of a control valve, connected with a source ofcompressed air and having a reciprocable piston which actuates a driver3,490,545 Patented Jan. 20, 1970 for driving the fasteners into aworkpiece. The cylinder has a bottom section with a fastener guidingnose structure. A shiftable trip means is arranged at the bottom sectionand normally projects a predetermined distance below the fastenerguiding nose of the tool. This trip means releases the trigger of thecontrol valve only if the nose structure of the machine in its operativeposition is pressed against the workpiece into which the fastener is tobe driven.

According to the invention this trip means has an upper end shaped likea piston, which in the inoperative position of the machine is under theinfluence of compressed air to keep the trip means in its blockingposition, and in the operative position communicates with the atmospherewhereby the trigger lever means of the control valve is released toallow the manual actuation of the trigger lever. The control valve, too,is pneumatically actuated.

Referring now to the drawings the invention will be described in detail.

The hand tool shown in FIGURES 1 and 2 of the drawings and whichembodies the invention is operated by compressed air and is adapted todrive staples, nails, pins or similar fastening means into a workpiece.The machine comprises a housing 1 consisting for instance of lightweightmetal and having a handle 2, which in its interior is constructed ascompressed air reservoir 3. In the head portion of housing 1 a cylinder5 containing a working piston 4 is arranged in a conventional manner.The compressed air from reservoir 3 is through a control valve assembly7 introduced into cylinder 5. The control valve assembly 7 ispneumatically operated by means of a trigger lever means 6. Connected tothe working piston 4 is a driver 8, which is guided in a drive track. Atits bottom section 9 the drive track has a fastener guiding nose 10. Thedrive track communicates in the usual manner with a magazine 11, inwhich the fasteners to be driven are housed. At the working stroke ofthe driver 8 the fasteners are driven into a workpiece through thefastener guiding nose 10 which is then placed immediately adjacent theworkpiece.

A trip member 12 consisting of a plate with a U-shaped profile isshiftably arranged at the front wall of the drive track. This tripmember projects in its inoperative position a predetermined distancebelow the fastener guiding nose 10 and is by way of a transverse arm 13connected with an extension piece 14. This extension piece 14 isenclosed by a housing plate 15, in which a pivot 16 for the triggerlever assembly 6 and a pin 17 are located. The pin 17 engages anelongated hole 18 which is located in the extension piece 14. On a pin19 of the extension piece 14 an angle lever 20 is pivotally mounted, atthe lower end of which two coaxial pins 21 are arranged, which engageinto longitudinal grooves 22 at the lower end of trigger lever 6. Thetrigger lever 6 has a U-shaped cross-section.

The upper end of extension piece 14 is shaped as a piston 23 which isarranged coaxially with the piston shaped lower end 24 of the valve stem25 of control valve 7, which piston shaped lower end 24 is shiftablylocated in a bore 26 passing through a partition of housing 1.

The piston shaped upper end 23 of extension piece 14 in all positionscloses the bore 26 and is sealed against the bore by a packing ring 27.The valve stem 25 extends across the compressed air reservoir 3 of thehousing and carries a lower stop means 28 and an upper stop means 29 forlimiting its movement. The piston shaped lower end 24 of the valve stem25 is sealed against the bore 26 by a packing ring 30. The bore 26communicates through a cross channel 31 and a bore 32, which is arrangedparallel to bore 26, with the compressed air reservoir 3. Cross channel31 is controlled by a preliminary valve, the control member of whichconsists of a valve piston 34, which is movable in the bore 32 and issealed against same by two O-rings 33, and which is resting in theinitial position on a stop pin 35. The bore 32 is through a passage 36in open communication with the compressed air reservoir 3. The lowerportion of valve piston 34 has a larger clearance in bore 32 and isprovided with a longitudinal groove into which the stop pin 35 engages.

The control valve assembly 7 actuates, in a known manner which is notexplained in detail, a piston-like main inlet valve 37 for introductionof compressed air to the working cylinder 5.

In the inoperative position of the tool, shown in FIG- URE 1, theseveral parts have the illustrated position. Trip member 12 projectsbeneath the fastener guiding nose 10 of the drive track. Trigger leverassembly 6 and working piston 4 are in their initial position. Thepreliminary valve piston 34 is in its lower final position, in which itrests on.

the stop means 35 so that the cross channel 31 is open. Thereby crosschannel 31 connects the air space in bore 26 between both pistons 23 and24 through bore 32 and passage 36 with compressed air reservoir 3.

The compressed air from the reservoir 3 on the one hand presses piston23 and thus trip means 12, 13, 14 downwards, and on the other hand valvestem 25 upwards, in which position control valve assembly 7 keeps closedthe main inlet valve 37 of the working cylinder 5.

In this position of trip means 12, 13, 14, the trigger lever assembly 6cannot move valve stem 25 of control valve 7 because angle lever 20cannot lift preliminary valve piston 34, so that compressed air from theair reservoir 3 flows into bore 26 and pushes both pistons 23, 24 apartfrom each other.

When the tool is placed in the operative position, in which the fastenerguiding nose 10 is pressed against the workpiece and thereby the feelerplate, i.e. trip member 12, is moved upwards, the extension piece 14with its piston 23 reaches its upper final position shown in FIG- URE 2.When the trigger lever assembly 6 is shifted in its operative positionit carries along the angle lever 20, the upper end of which is adjacentthe preliminary valve piston 34 and raises same until its lower endcontacts stop pin 35. In this position preliminary valve piston 34closes cross channel 31 against compressed air reservoir 3.

Thus the air space of bore 26 through cross channel 31 and the annularclearance between the lower portion of preliminary valve piston 34 andbore 32 communicates with the atmosphere. Due to the exhaustion of bore26 the valve stem 25 moves downwards, until its stop means 28 abutsagainst housing 1. Thereby the control valve assembly 7 is operated andsimultaneously causesactuation of the main inlet valve 37, Compressedair from the air reservior 3 is admitted to the working cylinder andactuates working piston 4, which effects firing of its working strokeand moves into the lower final position, shown in FIGURE 2, in whichposition the driver 8 has driven a fastener out of magazine 11 into theworkpiece.

When the tool is in its operative position with its fastener guidingnose placed adjacent the workpiece, immediately after manual actuationof the trigger lever assembly 6, control valve 7 pneumatically shiftsthe main inlet valve 37 into its open position whereby the compressedair is instantly admitted to the working cylinder 5 and actuates thepiston 4 to force the driver 8 downwardly through the drive track sothat a fastener is driven into the workpiece with a high strokeefiiciency.

On the other hand the working stroke can be fired also by moving thetool adjacent the workpiece with the trigger lever assembly manuallypivoted in its operative position, whereby a sequence of working strokesmay be fired by simply placing the tool adjacent the workpiece. In thismanner a high efficiency of the fastener applying tool may be performed.

The safety mechanism may also comprise the structure shown in FIGURES 3to 6, in which in lieu of the a g e lever 20 an intermedia e arm 51 iprovided on a 54. The upper end of extension piece 53 is shaped as apiston 55, which is guided in a bore 56. Bore 56 forms the lower portionof the coaxial bore 26 receiving the piston-like lower end 24 of valvestem 25 of the control valve assembly. Parallel with bore 26 is arrangedthe bore 32 containing the preliminary valve piston 34, which bore issurrounded by a sleeve 57 being inserted into the corresponding portionof the housing 1. Bore 56 communicates with bore 32 by a duct 58 in thewall of the housing and by several cross bores 59 arranged in the sameradial plane of sleeve 57. Bore 32 also communicates with the compressedair reservoir 3 via a nozzle 60.

When the trip member 54 is moved in its operative position as shown inFIGURES 4 and 6 by placing the fastener guiding nose of the tool againstthe workpiece, the trigger lever assembly 6 can be shifted quickly foractuating the control valve 7 as the intermediate arm 51 is closelyadjacent trigger lever 6 and is moved along without retardation when thetrigger lever is manually actuated and moved from the inoperativeposition of FIGURE 4 into the operative position of FIGURE 6, whichmovement by the intermediate arm 51 immediately is transferred to thepreliminary valve piston 34. This piston is then moved upwardly andinterrupts the communication of the air space of bore 56 between the twopistons 24 and 55 with the air reservoir 3. The air space of bore 56 isthen exhausted through the annular clearance of the lower portion ofpreliminary valve piston 34 and its sleeve 67, so that the valve stem 25due to the exhaustion of bore 56 reaches instantly its lower finalposition, in which the control valve 7 is actuated so as topneumatically open the main inlet valve 37, whereby compressed air isadmitted to the working cylinder 5.

The embodiment of FIGURES 3 to 6 in the same manner as the embodiment ofFIGURES 1 and 2 can be operated either by placing the fastener guidingnose of the tool against the workpiece or by manually actuating thetrigger lever assembly.

The nozzle 60 of the bore 32 causes the preliminary valve piston 34 tobe retracted to its initial position with retardation after a firingstroke so that an exact sequence of strokes is achieved and an actuationof the control valve 7 is prevented before the working stroke of piston4 is finished. Therefore the control valve 7 cannot be actuated before afastener is completely driven into the workpiece.

In a preferred embodiment the nozzle 60 is exchangeably secured in thecorresponding housing portion, whereby a change in the stroke sequenceof the working piston 4 can be obtained in a simple manner. The smallerthe passage cross section of nozzle 60, the more the rearward movementof the preliminary valve piston 34 in its initial position is retardedand thus the stroke sequence of the machine reduced. If a larger crosssection of the nozzle is chosen, the stroke sequence can be increased.

Besides, an optimum of reliability of operation is achieved by insertingthe nozzle 60 into the bore 32 of preliminary valve, as the stroke speedof the preliminary valve is adjusted to the speed of the working pistonand detrimental double strokes are avoided. Working with this machine isthus considerably improved, as the machine works calmly and practicallywithout recoil.

It will be understood that other modifications and embodiments may beprovided by those skilled in the art without departing from the spiritand scope of the present invention;

Our claims are:

1. In a" pneumatic fastener driving tool having a body containing aworking cylinder and piston and a compressed air reservoir, controlvalve means for regulating the passage of compressed air between saidreservoir and said working cylinder, a manually operable trigger foreffecting operation of said control valve means, and trip means movablebetween operative and inoperative positions, said trip means beingcooperable with said trigger for preventing operation of said controlvalve means except when said trip means is in said operative position inresponse to pressing of the tool against a workpiecej the improvementwhich comprises:

means defining a cylindrical air chamber in said body; a pair of pistonmembers at opposite ends of said chamber, one of said piston membersbeing connected to said trip means and the other of said piston membersbeing connected to said control valve means; and preliminary valve meansregulating the passage of compressed air between said reservoir and saidchamber;

said chamber communicating with said reservoir through said preliminaryvalve means in the inoperative position of said trip means for urgingsaid piston members apart, and said preliminary valve means beingshiftable by said trigger in the operative position of said trip meansfor blocking communication between said chamber and said reservoir andfor exhausting said chamber to the atmosphere.

2. The tool as claimed in claim 1, wherein said one piston membercomprises a piston-shaped extension portion of said trip means, saidcontrol valve means includes an elongated valve stem, said other pistonmember comprises a piston-shaped end portion of said valve stem, andsaid piston members are in opposed coaxial relation in said chamber.

3. The tool as claimed in claim 1, wherein said preliminary valve meanscomprises means in said body defining a bore parallel to said chamber,said bore communincating with said reservoir and with the atmosphere,air passage means extending between said chamber and said bore, and avalve piston movable in said bore in response to movement of saidtrigger.

4. The tool as claimed in claim 3, wherein said valve piston has oneportion sealed against said bore and another portion having a clearancewith said bore.

5, The tool as claimed in claim 4, wherein said air passage meanscomprises a cross channel extending between a central portion of saidbore and a central portion of said chamber intermediate said pistonmembers, said bore having one end portion in communication with saidreservoir and its other end portion in communication with theatmosphere, whereby, in one position of said valve piston, said chambercommunicates with said reservoir through said cross channel and said oneend portion of said bore, and, in another position of said valve piston,said chamber communicates with the atmosphere through said crosschannel, said clearance, and said other end portion of said bore.

6. The tool as claimed in claim 5, wherein stop means is provided forlimiting the movement of said valve piston between said one position andsaid other position.

7. The tool as claimed in claim 3, wherein a removable nozzle isprovided in said here for regulating the flow of air between saidreservoir and said bore, said nozzle being replaceable to vary the sizeof the air passage between said reservoir and said bore whereby to varythe stroke sequence of the tool.

8. The tool as claimed in claim 3, wherein said bore is provided with asleeve, said valve piston is reciprocable in said sleeve, and said airpassage means comprises at least one cross bore in the wall of saidsleeve.

References Cited UNITED STATES PATENTS 3,194,324 7/1965 Langas 17323,320,860 5/1967 Bade 91461 3,387,541 6/1968 Bade 91-461 ERNEST R.PURSER, Primary Examiner US. 01. X.R. 173-45; 91-461

